Why Is Physical Activity Important Even if Body Composition Doesn't Change?
Physical activity is important for health even if it produces no changes in body composition that is, even if a person remains overweight or obese. Physical activity confers benefits no matter how much you weigh; conversely, physical inactivity operates as a risk factor for health problems independently of body composition.
Regular physical activity and exercise block many of the destructive effects of obesity. For example, physical activity improves blood pressure, blood glucose levels, cholesterol levels, and body fat distribution. It also lowers the risk of cardiovascular disease, diabetes, and premature death. Although physical activity and exercise produce these improvements quickly in some people and slowly in others, due to genetic differences, the improvements do occur. Physical activity is particularly important for the many people who have metabolic syndrome or prediabetes, both of which are characterized by insulin resistance. Exercise encourages the body's cells to take up and use insulin efficiently for converting nutrients into usable energy. Being physically inactive for just one day decreases the capacity of the cells to take up and use blood sugar.
Although being physically active and not being sedentary may sound identical, experts describe them as different dimensions of the same health issue. Data suggest that it is important not only to be physically active but also to avoid prolonged sitting. In one study, people who watched TV or used a computer four or more hours a day had twice the risk of having metabolic syndrome as those who spent less than one hour a day in these activities; other studies reported similar results. Thus, in addition to increasing physical activity, avoiding or reducing sedentary behavior is an important and challenging health goal.
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Physical activity, then, is important even if it doesn't change body composition. But at a certain level, physical activity and exercise do improve body composition (meaning less fat and more lean muscle mass). Evidence supports a dose-response relation between exercise and fat loss: The more you exercise, the more fat you will lose. This includes both total body fat and abdominal fat. In addition, the more body fat a person has, the greater the loss of abdominal fat with exercise. Studies show that, even without calorie reduction, walking 150 minutes per week at a pace of four miles per hour, or jogging 75 minutes a week at six miles per hour, decreases total fat and abdominal fat and improves metabolic health.
Studies also show, however, that combining exercise with an appropriate reduction in calories is an even better way to reduce levels of body fat and increase lean muscle mass. The results of combining exercise and calorie reduction may not show up as expected on the scale because the weight of body fat lost is partially offset by the weight of muscle mass gained. Still, your body composition, physical fitness, and overall health have improved.
The question is sometimes asked: Which is more important in combating the adverse health effects of obesity physical activity or physical fitness? Many studies suggest that both are important; the more active and fit you are, the lower your risk of having health problems and dying prematurely. Of the two, however, physical activity appears to be more important for health than physical fitness.
Cardiometabolic risk factors and metabolic syndrome in the Aerobics Center Longitudinal Study. Mayo Clinics Proceedings 88(3): 259-270; Baer, H. J., et al. 2011. Risk factors for mortality in the nurses' health study: A competing risks analysis. American Journal of Epidemiology 173(3): 319-329; Stephens, B. R., et al. 2011. Effects of 1 day of inactivity on insulin action in healthy men and women: interaction with energy intake. Metabolism Clinical and Experimental 60: 941-949. large-scale population surveys. Obesity is defined as a more serious degree of overweight that carries multiple major health risks. The cutoff point for obesity may be set in terms of percent body fat or in terms of some measure of total body weight.